The present invention relates to fireworks displays and, more particularly, to a new method and system of presenting precision fireworks displays with a decreased environmental impact.
"Pyrotechnics" is the "science of fire." Pyrotechnic displays, commonly referred to as fireworks or fireworks displays, have been created and enjoyed for centuries by millions of people. Over the years, the systems and methods for creating the displays have remained substantially unchanged.
The fireworks systems of the prior art are comprised essentially of two main components, namely a pyrotechnic projectile and a mortar for directing the pyrotechnic projectile into the air. The pyrotechnic projectile itself consists of two principal components, comprising an initial burst and a main burst. Black powder is one of the oldest pyrotechnic propulsion agents and it is typically used as the initial burst and main burst component. The main burst also includes pellets of color composition known as "stars." Igniting the stars during detonation of the main burst provides the light and color of the fireworks display.
Common pyrotechnic projectiles comprise an inner shell and an outer shell. To preserve the main burst until aerial ignition, the main burst is enclosed within the inner shell, while the initial burst is enclosed within the outer shell. The pyrotechnic projectile also has two fuses in the form of an initial fuse and a main fuse. The main fuse extends from the initial burst in the outer shell to the main burst in the inner shell. The initial fuse extends from the initial burst to the exterior of the outer shell. By igniting the initial fuse, the initial burst is exploded and propels the pyrotechnic projectile from the mortar into the air. Contemporaneously, the main fuse is lit because the end of the main fuse protrudes into the initial burst. The main fuse then takes a specific time to burn into and ignite the main burst.
The pyrotechnic projectile can take on various shapes. For cylindrical shells, the main burst includes stars which are randomly packed. Upon detonation of the main burst, the shell opens, and the stars are ignited in an irregular visual pattern. For round shells, the main burst consists of the stars arranged around a central core of black powder. When the main burst of the round shell is ignited, the stars are distributed in a round, symmetrical pattern. Sometimes the shell will contain a flash-and-sound powder, instead of stars, to produce a flash of light and a loud noise.
Factors in raising the pyrotechnic projectile to a particular altitude are aerodynamic drag, projectile stability and the size of the initial burst. In this regard, pyrotechnic projectiles are usually hand manufactured, and various materials have been used to form the pyrotechnic projectile's outer shell, including paper and plastics. The manufacturing variations, therefore, can cause uncertainties in the final shape of the pyrotechnic projectile. Hence, such manufacturing variations can create an outer shell that is non-uniform in shape, which causes undesirable drag and instability in flight. As a result, the altitude to which the pyrotechnic projectile is launched can never be determined with precision. In addition to the structural variations in the pyrotechnic projectile outer shell structure, the variations in the quality and composition of the black powder charge used in the initial burst can propel otherwise identical projectiles to various different heights. This is explained in more detail below.
A further related factor regarding altitude is the main fuse technology, which governs detonation timing of the main burst after ignition of the initial burst. The main fuse, used to detonate the main burst of the pyrotechnic projectile, typically is a delayed chemical fuse. Existing chemical fuses are usually non-uniform in their construction and therefore exhibit a wide variation in their burn rate from one pyrotechnic projectile to the next. As a result, it has been found that a pyrotechnic projectile set to detonate at approximately 600 feet in the air may detonate anywhere from between 500 feet and 700 feet, roughly a 16 percent deviation.
Variations in black powder composition, black powder quality, pyrotechnic projectile structure and mortar structure all contribute to the inherent lack of uniformity of projectile height and position at the time of shell ignition. Amounts of black powder in the initial burst, length and orientation of the initial and main fuses, and composition and thickness of the shell casings are only within tolerances obtainable during non-precision hand manufacturing. Because of the lack of precise repeatability during pyrotechnic projectile manufacturing, large variations between the pyrotechnic projectile's ignition time and flight path from pyrotechnic projectile to pyrotechnic projectile are the norm. Historically, fireworks displays have not been precise, repeatable or accurate. However, although it is not possible to exactly duplicate any one display, by using different types of stars and/or flash-and-sound powder, and by arranging them in the shell in a particular way, various types of fireworks displays can be created when a variety of such pyrotechnic projectiles are ignited simultaneously or in series.
From the foregoing, it can be seen that the typical pyrotechnic projectile is a self-contained unit having its means of propulsion (i.e., the initial burst) and mechanism for timing projectile detonation (i.e., the initial and main fuses) incorporated into its structure. As such, these propulsion and timing mechanisms are fixed by the structural composition of the pyrotechnic projectile, which is pre-set at the factory. Hence, it is not possible to adjust those parameters once the manufacturing process for the pyrotechnic projectile has been completed.
Accordingly, it further can be seen that the launch and detonation of existing pyrotechnic projectiles is an inexact science and is subject to severe limitations and drawbacks. To determine the pyrotechnic projectile path and altitude achieved, the amount of black powder in the initial burst is significant, since a greater amount of black powder generates a larger gaseous expansion within the mortar behind the pyrotechnic projectile and a resultant higher projection into the sky. The limitation on the height of the projection is based on the minimum burn rate of the black powder, inasmuch as the rate of pressure increase cannot exceed that which the inner shell can withstand, i.e., structural integrity of the inner shell of the pyrotechnic projectile must be maintained.
For any given size of shell there is a practical limit to the altitude that can be reached using black powder as the initial burst component. Increasing the altitude requires increasing the acceleration rate up the length of the mortar, and therefore increasing the burn rate of the initial burst. However, as the initial burst is formulated to burn faster, it becomes less controllable; as the rate of pressure rise increases, the initial burst is consumed quicker and begins to exhibit explosive detonation characteristics. The result is an exponential pressure rise that will destroy a pyrotechnic projectile in the mortar.
Increasing the force which the inner shell casing can withstand, for example, by increasing the shell thickness, causes a change in the pyrotechnic projectile's performance. This change in performance, which can cause a change in the characteristics of a fireworks shell, is disfavored because it usually diminishes and/or alters the visual display quality. Consequently, the projection height of the pyrotechnic projectile is limited by the durability of the shell. Historically, it was not possible to project the pyrotechnic projectile beyond a certain height, relative to its diameter. For example, a pyrotechnic projectile having a nominal six inch shell casing typically can be launched to an altitude of between about 200-600 feet, with 600 feet being the practical limit. A pyrotechnic projectile having a smaller shell casing will go lower and one with a larger casing will go higher, with 1,000 feet being about as high as they will go.
As noted above, the pyrotechnic projectiles are directed into the air through the mortars. The mortars are cylindrical in shape. To propel the pyrotechnic projectile from the mortar, the pyrotechnic projectile is placed in the mortar. The mortars can be constructed of any rigid material such as convolute paper, metal or plastic. The pyrotechnic projectile has a specific orientation within the mortar. The orientation provides for the outer shell having the initial burst to be arranged so that it is below the main burst. This type of fireworks display system also produces a loud noise, from detonation of the initial burst, requiring ear protection at the launch site. There is no existing method of noise reduction for the prior art devices. Moreover, existing mortar construction generally is not conducive to adjustment after installation at the launch site to enable aiming of the pyrotechnic projectile to different locations in the sky.
Another drawback associated with existing pyrotechnic projectiles and mortars is their adverse impact on the environment. For example, the current method of projection using a charge of black powder forms a residue having a detrimental environmental impact on the ground and any water area in and around the firing site. The black powder, products of combustion, and products of incomplete combustion from the pyrotechnic projectile firing are extremely corrosive agents (e.g., various salts that form acids with rain or dew). These materials, in addition to corroding the existing equipment at the site, are deposited in the area surrounding the mortar site, both on the ground and in the water. There are significant adverse effects from this deposition of sulfuric acid and other harmful chemicals on the soil and water surrounding the site. Moreover, on the ground, at the time of firing, there are large quantities of smoke. This smoke can be very distracting to the guests and may direct their attention away from the aerial fireworks display. In addition, large quantities of smoke may be blown by the wind toward the guests, causing further irritation and in some cases causing a visual obstruction.
Fallout from the pyrotechnic projectile after it has been detonated in the air creates further environmental concerns. Firework shell casings are traditionally made from laminated paper or plastic. Paper casings have been in use since the time of Marco Polo, whereas plastic casings were introduced approximately 25 years ago. Existing pyrotechnic projectile shells are not usually completely fragmented and consumed in the air during detonation of the pyrotechnic projectile into its intended display. Instead, the shells are incompletely fragmented, and many portions of the shell, some of them quite large, fall back to the ground. This creates undesirable litter in an area below the point of the fireworks display. Portions of the shell falling back to the ground also cause a safety hazard to people on the ground who could be hit and injured by the fallout. Moreover, after detonation, portions of the shell can and often do fall back to the ground as burning debris. This causes a severe fire hazard in many areas.
In spite of the inability to precisely control fireworks displays, no change from the existing system has ever been successful because of the inability to detonate the main burst of the pyrotechnic projectile by means other than ignition by the initial burst. As previously discussed, because the black powder provides the propelling charge necessary to ignite the main fuse of the pyrotechnic projectile, use of any other type of propulsion means that does not incorporate black powder or its equivalent does not provide for delayed aerial detonation.
In view of the inaccuracy and drawbacks possessed by existing pyrotechnic projectiles and mortars, serious limitations are imposed on the versatility of the resulting pyrotechnic display. For example, the limited capability to aim the pyrotechnic projectile and control its trajectory inhibits the ability to send a pyrotechnic projectile to different locations of the sky having different altitudes. The lack of precision and timing regarding detonation of the projectile in the air prevents precise timing of the main burst explosion. Moreover, fireworks shows cannot be precisely presented in synchronization with programmed material, such as music and dialogue, nor is it possible to repeatably and consistently produce a fireworks pattern corresponding to a recognizable shape, in view of the inaccurate and random nature of firing of the main burst. The relatively high volume of black powder used in the initial burst, as well as the main burst, also requires that the projectile be treated with special care and handling during transportation. In this regard, there are strict statutory shipping requirements for hazardous materials which govern the handling and transportation of the pyrotechnic projectiles. These factors consequently increase fireworks display expense.
Accordingly, there has existed a definite need for a method and system for launching and detonating projectiles which is more accurate, safe and versatile, with a minimum adverse environmental impact. The present invention satisfies these and other needs, and provides further related advantages.